Flow mixing device for an exhaust after-treatment system

ABSTRACT

A flow mixing device includes a body having a first end, a second end, and an interior volume defined between them. An inlet plate, coupled to the first end of the body, defines at least two inlet orifices in fluid communication with the interior volume. Similarly, an outlet plate, coupled to the second end defines an outlet passage of the flow mixing device. A diffuser conduit, coupled to the inlet plate, defines an inlet passage disposed in fluid communication with the respective inlet orifices. A separator plate assembly disposed in the interior volume extends partially between the first and second ends of the body. Flow guiding vanes, coupled proximal to the second end, extend partially within the diffuser conduit.

TECHNICAL FIELD

The present disclosure relates to an exhaust gas after-treatment systemof an internal combustion engine. More particularly, the presentdisclosure relates to a flow mixing device of the exhaust gasafter-treatment system.

BACKGROUND

Internal combustion engines have been typically known to employ exhaustafter-treatment systems to lower or reduce undesired emissions in anexhaust stream. One of the undesired emissions in the exhaust stream mayinclude nitrous oxides (NO_(x)). A Selective catalytic reduction (SCR)system may be additionally utilized to reduce the quantity of NO_(x)emissions in the exhaust stream. The SCR system is configured to injecta reductant such as urea in the exhaust stream to convert harmful NOxemissions into harmless nitrogen and water.

A flow mixer may be used to combine multiple exhaust streams generatedfrom the internal combustion engine into a single exhaust stream priorto injection of a reductant. A uniform mixing of the exhaust gases isrequired to maximize flow uniformity and minimize backpressure prior toentry of the exhaust gases at the reductant injection location.

U.S. Pat. No. 8,814,969 discloses an exhaust gas emission control systemfor an internal combustion engine. The exhaust gas emission controlsystem includes a cylindrical body through which the exhaust flows. Thecylindrical body has an inflow pipe and an outflow pipe. The inflow pipeincludes a louvre member defining a plurality of slits having varyingheight. A height of the slits decreases on moving away from a center ofthe inflow pipe. Although the louvre member may provide a uniform flowand minimize backpressure to an extent, it does not uniformly mix twoseparate exhaust streams into a single exhaust stream for effectivelyreducing NOx.

Hence, there is a need for an improved system that provides uniformmixing of multiple exhaust streams into a single exhaust stream whilealso minimizing backpressure and maximizing flow uniformity.

SUMMARY OF THE DISCLOSURE

In an aspect of the present disclosure, a flow mixing device for anexhaust after-treatment system of an internal combustion engine includesa body having a first end and a second end disposed distally away fromone another. The body defines an interior volume. The flow mixing devicefurther includes an inlet plate coupled to the first end of the body.The inlet plate having at least two inlet orifices formed therein influid communication with the interior volume, Further, an outlet plateis coupled to the second end of the body. The outlet plate defines anoutlet passage in fluid communication with the interior volume. The flowmixing device further includes a diffuser conduit releasably coupled tothe inlet plate and disposed around each of the inlet orifices. Thediffuser conduit configured to define an inlet passage disposed in fluidcommunication with the inlet orifices of the inlet plate and theinterior volume of the body. The flow mixing device further includes aseparator plate assembly includes a first separator plate and a secondseparator plate, the first and second separator plates coupled at anangle relative to each other at the first end of the body and convergingtowards a longitudinal plane defined between the pair of diffuserconduits. The flow mixing device further includes multiple flow guidingvanes coupled to the body proximal to the second end and configured toextend at least partially within the diffuser conduit.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic representation of an engine system having a flowmixing device that is used to combine multiple exhaust streams exitingfrom an internal combustion engine prior to entering a SelectiveCatalytic Reduction system, in accordance with an embodiment of thepresent disclosure;

FIG. 2 is a front perspective view of the flow mixing device, inaccordance with an embodiment of the present disclosure;

FIG. 3 is a rear perspective view of the flow mixing device from FIG. 1;

FIG. 4 is a front view of the flow mixing device of FIGS, 2-3;

FIG. 5 is an isometric view of the flow mixing device of FIGS. 1-4 takenalong a section plane AA′ of FIG. 4;

FIG. 6 is a rear perspective view of the flow mixing device, inaccordance with another embodiment of the present disclosure; and

FIG. 7 is an isometric view of the flow mixing device from FIG. 6 takenalong a section plane CC′ of FIG. 6

DETAILED DESCRIPTION

Wherever possible, the same reference numbers will be used throughoutthe drawings to refer to same or like parts. Moreover, references tovarious elements described herein are made collectively or individuallywhen there may be more than one element of the same type. However, suchreferences are merely exemplary in nature. It may be noted that anyreference to elements in the singular may also be construed to relate tothe plural and vice-versa without limiting the scope of the disclosureto the exact number or type of such elements unless set forth explicitlyin the appended claims.

As shown in FIG. 1, an engine system 100 includes an engine 102 and anafter-treatment system 104 to treat exhaust streams 106 produced by theengine 102. The engine 102 may include other features not shown, such ascontrollers, fuel systems, air systems, cooling systems, peripheries,drivetrain components, turbochargers, exhaust gas recirculation systems,etc.

The engine 102 may be any type of engine (internal combustion, gas,diesel, gaseous fuel, natural gas, propane, etc.), may be of any size,with any number of cylinders, and in any configuration (“V,” in-line,radial, etc.). The engine 102 may be used to power any machine or otherdevice, including on-highway trucks or vehicles, off-highway trucks ormachines, earth moving equipment, generators, aerospace applications,locomotive applications, marine applications, pumps, stationaryequipment, or other engine powered applications.

As shown in the embodiment of FIG. 1, the after-treatment system 104includes two exhaust conduits: a first exhaust conduit 110 and a secondexhaust conduit 112. Each of the first and second exhaust conduits 110,112 includes one or more of the following: a Diesel Oxidation Catalyst(DOC) 114 and a Diesel Particulate Filter (DPF) 116. The DOC 114oxidizes Carbon Monoxide (CO) and unburnt hydrocarbons (HC) into CarbonDioxide (CO2). The DPF 116 collects particulate matter or soot. The DOC114 and the DPF 116 may be packaged in the same canister as shown, orseparately from each other.

Exhaust gases 106 from the first and second exhaust conduits 110, 112are passed through a flow mixing device 118 to combine the two separateexhaust streams 106 into a single combined exhaust stream 120. As shownin the embodiment of FIG. 1, the DOC 114 and the DPF 116 can be locatedupstream of the flow mixing device 118 and within the first and secondexhaust conduits 110 and 112. However, in various embodiments, the firstand second exhaust conduits 110, 112 may not include either the DOC 114or the DPF 116. In an embodiment, at least one of the DOC 114 and DPF116 may be located downstream of the flow mixing device 118. A SelectiveCatalytic Reduction (SCR) system 122 is provided to reduce NO emissionsin the combined exhaust stream 120 downstream of the flow mixing device118.

The SCR system 122 includes a reductant supply system 124 and an SCRcatalyst 126. The reductant supply system 124 can include one or more ofthe following: a reductant 128, a reductant source 130, a pump 132, avalve 134 and an injector 136. The reductant 128 is drawn from thereductant source 130 via the pump 132 and delivery to the injector 136that is controlled via the valve 134. The flow of reductant 128 may alsobe controlled by operation of the pump 132. While other reductants 128are possible, urea is the most commonly used reductant 128. Reductant128 decomposes or hydrolyzes into ammonia (NH₃) and is then adsorbed orotherwise stored in the SCR catalyst 126. The SCR catalyst 126, provideddownstream of the injector 136, includes a catalyst material disposed ona substrate. The substrate may consist of cordierite, silicon carbide,other ceramic, or metal. The substrate may include a plurality ofthrough going channels and may form a honeycomb structure.

After passing through the SCR system 122, the exhaust stream 120 may becirculated back to an exhaust gas recirculation system (not shown), aturbocharger (not shown) or discharged in atmosphere.

FIG. 2 shows a perspective view of the flow mixing device 118, accordingto an embodiment of the present disclosure. The flow mixing device 118is formed from a body 138 of any regular or irregular geometric shape,such as a polyhedral body. For example, the body 138 can includemultiple polygon faces joined together. The polygon faces at the top andthe bottom of the body 138 may be arranged such that an interior volumeof the flow mixing device 118 increases in the direction of flow of theexhaust gases. The polygon faces at the sides of the body 138 may bearranged such that the volume of the flow mixing device 118 may decreasein the direction of flow of the exhaust gases. The polygon faces of thebody 138 may be sheet metal parts formed by a stamping process. Thestamped sheet metal parts may have tabs at ends which may fit intocorresponding inserts provided in complementary parts. After assemblingthe flow mixing device 118 through tabs and inserts, welding or anyother joining process may be used to provide final shape to the body138. The polygon faces may also be formed by bending sheet metal partsinto suitable shapes. Shapes of sheet metal parts may be varied to suitthe needs of different applications. Though, in the present embodiment,the body 138 is explained as made up of stamped sheet metal parts orbent sheet metal parts, it may be evident to a person of ordinary skillin the art that any other suitable material and processes may be used toprepare the body 138.

As shown in FIG. 2, the body 138 has a first end 140 and a second end142 located distally away from the first end 140. Further, an inletplate 144 is affixed at the first end 140 of the body 138. The inletplate 144 may be a sheet metal part prepared in the same manner as thebody 138. In an embodiment, the inlet plate 144 may have tabs andinserts through which the inlet plate 144 may be affixed to the body 138proximal to the first end 140. The inlet plate 144 defines at least twoinlet orifices: a first inlet orifice 146 and a second inlet orifice148. The first inlet orifice 146 and the second inlet orifice 148 can becoupled to a first diffuser conduit 150 and a second diffuser conduit152, respectively, through stiffener rings 154 and 156 provided on theinlet plate 144 along the periphery of the first and second inletorifices 146, 148. In various embodiments, the diffuser conduits 150,152 are coupled to the inlet plate 144 through any other means known inthe art.

The first and the second diffuser conduits 150, 152 define a first inletpassage 158 and a second inlet passage 160, respectively. Each of thefirst and the second inlet passages 158, 160 is in fluid communicationwith the respective first and the second orifices 146, 148. Exhauststream 106 flowing through the first exhaust conduit 110 is received atthe first inlet passage 158 and passes on to the first inlet orifice146, through the first diffuser conduit 150. Similarly, the exhauststream 106 flowing through the second exhaust conduit 112 is received atthe second inlet passage 160 and passes on to the second inlet orifice148, through the second diffuser conduit 152.

As shown in FIG. 3, the flow mixing device 118 includes an outlet plate162 affixed at the second end 142 of the body 138. The flow mixingdevice 118 is substantially hollow and defines an interior volumebetween the inlet plate 144 and the outlet plate 162. The interiorvolume is in fluid communication with the first and the second inletpassages 158, 160 and an outlet passage 163 defined by the outlet plate162.

The flow mixing device 118 has a first inner surface 164 and a secondinner surface 166. The first inner surface 164 and the second innersurface 166 are mutually opposed to each other and extend between theinlet plate 144 and the outlet plate 162.

The flow mixing device 118 further includes a separator plate assembly168. The separator plate assembly 168 is located in the interior volumecoupled to the body 138. As shown in the sectional view of FIG. 5, takenalong a section AA′ of FIG. 4, the separator plate assembly 168 includesa first separator plate 170 and a second separator plate 172. The firstand the second separator plates 170, 172 are coupled to an insidesurface of the inlet plate 140 and extending toward the second end 142.The first and the second separator plates 170, 172 are inclined to eachother at an angle ‘α’, and form a substantial V shape towards the secondend 142 of the body 138. Further, the separator plate assembly 168extends from the first inner surface 164 to the second inner surface166. The first and second separator plates 170, 172 may intersect eachother at a longitudinal plane BB′. The plane BB′ may extendlongitudinally between the first and second ends 140, 142. In oneembodiment, the plane BB′ may be located symmetrically between the firstand second diffuser conduits 150, 152. In another embodiment, the planeBB′ is located at an offset towards any of the first and the seconddiffuser conduits 150, 152. Also, the plane BB′ may be orthogonal to theinlet plate 144. The separator plate assembly 168 ensures gradual anduniform mixing of exhaust gases from the first and the second diffuserconduits 150, 152.

Further, the flow mixing device 118 includes multiple flow guiding vanes174 located in the interior volume and on either side of the separatorplate assembly 168. The flow guiding vanes 174 extend from the first end140 of the body 138 to the second end 142 of the body 138. The flowguiding vanes 174 extend longitudinally between the first inner surface164 and the second inner surface 166. In an embodiment, the flow guidingvanes 174 may also extend partway between the first and second innersurfaces 164, 166. In another embodiment, the flow guiding vanes 174 mayextend fully between the first inner surface 164 and the second innersurface 166.

As shown in the embodiment of FIG. 5, the flow guiding vanes 174 canhave a first longitudinal portion 176, an inclined portion 178 and asecond longitudinal portion 180. The inclined portion 178 is inclined atan angle between both the first and the second longitudinal parts 176,180. The first and the second longitudinal parts 176, 180 have upperends located at planes of different elevation. The first longitudinalpart 176 continues to extend longitudinally partway inside the diffuserconduits 150, 152. The inclined portion 178 may be parallel to theincline angle of either of the first and second separator plates 170,172. In another embodiment shown in FIG. 7, taken along a sectionalplane CC′ of FIG. 6, the flow guiding vanes 174 have one longitudinalpart 182 and a slant part 184. The longitudinal part 182 and the slantpart 184 are inclined at an angle to each other. The longitudinal part182 extend partially inside the diffuser conduits 150, 152. The slantpart 184 may be parallel to either of the first and second separatorplates 170, 172.

With continued reference to FIGS. 3-5, the flow guiding vanes 174 arecoupled to a first pair of horizontal plates 186 and a second pair ofhorizontal plates 188. Specifically, each of the second longitudinalportions 180 of the flow guiding vanes 174 can be coupled to the firstand second pair of horizontal plates 186, 188. In another embodiment, asshown in FIG. 7, each of the slant parts 184 of the flow guiding vanes170 can be coupled to the pair of horizontal plates 186, 188. The firstand second pair of horizontal plates 186, 188 are fixedly coupled to athird inner surface 190 and a fourth inner surface 192 of the flowmixing device 118 and extend towards the separator plate assembly 168.The pair of first and second horizontal plates 186, 188 may providestructural rigidity to the flow guiding vanes 174 and help in avoidingany break off or vibration due to flow of exhaust streams 106. Also, thepair of first and second horizontal plates 186, 188 safeguard flowguiding vanes 174 against being cantilevered by their own weight.

In an embodiment as shown in FIG. 6 and FIG. 7, the flow mixing device118 additionally may include a perforated plate 194 coupled to theoutlet plate 162. As shown in FIG. 6, the perforated plate 194 caninclude one or more flanges 195 that may couple with the outlet plate162. In an embodiment, the outlet plate 162, and the perforated plate194 including the flanges 195 may be manufactured from the same sheetmetal part.

The perforated plate 194 is further supported on the outlet plate 162through a cross member 196. The cross member 196 is a structural elementthat may include two sheet metal bars joined together in an intersectingmanner so as to form a support structure for the perforated plate 194.The perforated plate 194 is coupled to the cross member 196 along thelength of the two bars. Also, the perforated plate 194 is located aroundthe center of the second end 142 leaving an open space 198 between theperiphery of the perforated plate 194 and the outlet plate 162. Further,in an embodiment, the perforations provided in the perforated plate 194may be uniform in size. Alternatively, the perforations may vary in sizeand in proportion to the distance from a center of perforated plate 194.

INDUSTRIAL APPLICABILITY

The flow mixing device 118, explained in the present disclosure,minimizes a backpressure while mixing two or more exhaust streams andoutput a single exhaust stream. Further, the flow mixing device 118helps in maintaining a desired flow profile of the exhaust stream priorto injection of the reductant. The flow mixing device 118 helps inproviding the exhaust stream a low velocity profile at center whichallows the reductant to be injected substantially symmetrically anduniformly.

In order to explain functioning of the flow mixing device 118, referencewill now be made to FIGS. 1-5. The flow mixing device 118 receives theexhaust stream 106 flowing through the first exhaust conduit 110 at thefirst inlet passage 158 defined by the first diffuser conduit 150.Similarly, the exhaust stream 106 flowing through the second exhaustconduit 112 is received at the second inlet passage 160 defined by thesecond diffuser conduit 152.

After passing through the first and the second diffuser conduits 150,152, the exhaust stream 106 from the first and the second exhaustconduits 110, 112 flow across the flow guiding vanes 174. As the flowguiding vanes 174 have one or more bends, the exhaust stream 106gradually change flow directions along the bends. Thereafter, exhauststreams 106 from the first and second. exhaust conduits 110, 112 mixwith each other to form the combined exhaust stream 120. Uniform flowprofile of the combined exhaust stream 120 is provided by the separatorplate assembly 168 and the flow guiding vanes 174 effecting gradual anduniform mixing of the exhaust streams 106 from the two exhaust conduits110, 112.

In another embodiment of the current disclosure as shown in FIGS. 6-7,the flow mixing device 118 additionally includes a perforated plate 194coupled to the outlet plate 162 of the body 138 and further supportedthrough the cross member 196. After the exhaust streams 106 from thefirst and second exhaust conduits 110, 112 pass through flow guidingvanes 170, the combined exhaust stream 120 pass through the perforatedplate 194. The perforated plate 194 has perforated structure which maycause the combined exhaust stream 120 to have a further uniform flowprofile. Also, as shown in the FIGS. 6 and 7, the perforated plate 194is located around the center of the second end 142 leaving open space198 between the periphery of the perforated plate 194 and the outletplate 162. Thus, larger volume of the combined exhaust stream 120 flowsfrom the periphery as compared to that flowing through the perforatedplate 194. As larger volume of the combined exhaust stream 120 flowsthrough the open space 198, around the peripheral region of theperforated plate 194, the velocity flow profile at the circumferentialregions is higher as compared to the velocity flow profile at the centerof the combined exhaust stream 120 exiting from the outlet passage 163.Such flow profile is desired to achieve a more uniform mixing ofreductant 128 with the combined exhaust stream 120.

While aspects of the present disclosure have been particularly shown anddescribed with reference to the embodiments above, it will be understoodby those skilled in the art that various additional embodiments may becontemplated by the modification of the disclosed machines, systems andmethods without departing from the spirit and scope of what isdisclosed. Such embodiments should be understood to fall within thescope of the present disclosure as determined based upon the claims andany equivalents thereof.

What is claimed is:
 1. A flow mixing device for an exhaustafter-treatment system of an internal combustion engine, the flow mixingdevice comprising: a body having a first end and a second end disposeddistally away from one another, the body configured to define aninterior volume therein; an inlet plate coupled to the first end of thebody, the inlet plate having at least two inlet orifices formed thereinin fluid communication with the interior volume; an outlet plate coupledto the second end of the body, the outlet plate defining an outletpassage in fluid communication with the interior volume; a diffuserconduit releasably coupled to the inlet plate and disposed around eachof the inlet orifices, the diffuser conduits configured to define aninlet passage disposed in fluid communication with the inlet orifices ofthe inlet plate and the interior volume of the body; a separator plateassembly comprising a first separator plate and a second separatorplate, the first and second separator plates coupled at an anglerelative to each other at the first end of the body and convergingtowards a longitudinal plane defined between the pair of diffuserconduits; and a plurality of flow guiding vanes coupled to the bodyproximal to the second end and configured to extend at least partiallywithin the diffuser conduits.
 2. The flow mixing device of claim 1further including a perforated plate coupled to the outlet plate of thebody, the perforated plate configured to allow a substantially uniformflow profile of a fluid exiting the body.